Protractor compass



Feb. zo, 1951 W, F KLEMM 2,542,537

PROTRACTOR-COMPASS Filed 001'.. 4, 1945 /(B L i f INVENTOR. ci BY E.MMM; 2%? yZ-Q *ed position. .lsed its" Atp any one-sixteenth of an inchlocation quickly l and accurately. An aperture in the slide for retheslide.

Patented Feb. 20, 1951 z UNITED STATES 'ffPAT'ENT OFFICE f .2,542,537 AY i v PRo'rRAo'roR COMPASS William F. Klemn, Detroit, Mich. Applicationoctober 4, 1945, seraINo. 6201.354

1 Claim. (Cl. {t3-@27)l [This invention relates to engineering scales f'and particularly to av scale for producing circles of any desireddiameter.

The scale of the present invention may be made of any material butpreferably is made oi Aa transparent resin material of rectangular shape*having one end of semicircular form. The center "of the semicircularend is preferably disposed 4 on a tab which is cut from the body of thesheet 'and formed to project thereabove.

'apart so that circles varying M3 in diameter may be struck about thecentral pin. The pin being I' 4secured in the transparent material maybe accurately located on the surface on which the circle gis to bestruck. Additional apertures of varying diameters are also providedthrough the body of the material for drawing circles of small diameterranging from 1/8" to l".

Protractor divisions may be provided on the arcuate end of the scale anda linear scale may be provided along one edge thereof.

A In a further form of the invention a springpressed pin may be mountedon a hub on the 1 center of the semicircula'r end having cutaway n lportions formingan aperture through which the 11. point of the pin isvisible from the top scale. .The point may be accurately located on thesur- ;face on which the circle is to be drawn irrespec- 1. 1tive ofwhether or not the material of the scale transparent. i j In a' furtherform which the invention may as- 'jsp-ine,- an elongated recess'isprovided in the lower face 'of the body portion for receiving a slidewhich ,w is adjusted therein above. the surface upon which r the `scaleis located. Serrations may be provided l on the under side of the of theslide for accurately positioning the slide Y in the recess.

through the slide and slot in the portion` fail-love theY recess forsecuring the slide in adjust- The serrations are preferably disrecessand on the top A bolt having a nutv thereon proapart so that theV slidemay be shifted ceiving the pencil point isl located relative tocentering element after the slide has been adjust..

ved relative to the scale 'by placingl the point of the pencil in theaperture in the slide and rotating' the point about thecenteringelement.

A sem'ispherical element of transparent mate'- rial having a 'center andconcentric rings scribed on the plane face thereof may be employed asthe centering' element about which the scale may be revolved." 'In anyof the constructions a scale is provided having a centering elementwhich may be quickly located'on a point about which a' circle is to bestruck. A circle of any desired r`diameter within 'the range of thescale vmay be drawn about a center through the application of the pointvof `a pencil in an aperture located a predetermined distance from thecentering' element which will vbe equal to the radius oi the circledescribed.

Accordingly, the main objects of theV invention are: to provide a scale-iordrawing' circles about a' center' having a 'projecting tab on whicha center is located about which the scale may be rei volved; to locate aplurality of rows of apertures in offset relationfor receiving the pointof a pencil' and disposed in le" increments from the een# ter about'which the scale is rotated; to provide a recess in the scale body havinga slide containingan aperture' therein which is adjustable relative to acentering element by which the radius of a circle 'is accurately locatedonv the scale; to provide a magnifying centering element about 'whichtheV scale may be revolved; and, in general', to provide a scale fordrawing' circles of any desired diameter within the scale range whichV`issimple ineen-struction, positive of operation and economicalotmanufacture.

v"tller objects and features of `novelty of the invention will bespecifically pointed out o' will become v'apparent when referring', fora betterunderstandin'g of the invention, Vto the following'descriptiontaken in conjunction with the Vaccomapanying drawing,A wherein:

The circle may be struck about the Figure 1 is a plan view of anengine'erin'g'A scale embodying features of this invention;

lig. 2 A`is an enlarged broken sectional view of the structureillustrated i'n Fig. l. taken onthe line 2 2 thereof;

Fig'. 3 is a view of structure. similar to that .illustrated in Fig. 2showing a modied form of the invention; y A e Fig. 4 is a sectional viewof the structure illustrated in Fig. 13, taken on the line 4 4 thereof;l

Q Fig'. 5 is 'an enlarged sectional view of the struc--turefillustrated, in Fig. .4, taken on the. line. 5 5

thereof;

Fig. 6 is a view of structure, similar to that illustrated in Fig. l,showing a further form which the invention may assume;

Fig. 7 is an enlarged sectional view of the structure illustrated inFig. 6, taken on the line 'I-l thereof;

Fig. 8 is an enlarged sectional view of the structure illustrated inFig. 7, taken on the line 8-8 thereof;

Fig. 9 is a View of structure, similar'to that illustrated in Fig. 1,showing a further form of the invention; and

Fig. 10 is an enlarged sectional view of them f illustrated in Figs. 1and 2.

structure illustrated in Fig. 9, taken on the line Ill-IB thereof.

Referring to Figs. 1 and 2, a scale in' is iuustrated having paralleledges I I and I2 joined at one end by a straight edge I3 and at theother end by a semicircular edge I4. The center-of lthe semicircularedge i'slocated at I5 on a tab .i5 formed inthe l`sheetlofnxaterial .ibythe U- shaped slot I'I cut therein; :The sheet of `rnaterial ispreferably made of transparent material embodying a certain amount ofresiliency. A tab I 6 is reversely bent at I3 to project up- .'wardlv atan angle from the plane .of the scale, as illustrated more specificallyin Fig. 2. A centering pin I9 is mounted on the center I5 of thetab..the point of which is maintained substan-` tially in the plane-ofthe lower surface of the scale or slightly thereabove.

'.The transparency of the material of the tab 15, as well as the slot-I1thereabout, permits the .point of the pin IB to be accurately located onthe point of a surface upon which a circle is to be" struck. Forlocatingrv the nencil point relative to the center I5, a plurality ofapertures 2l are provided in rows 22 in oblique relation so as .to belocated in increments'e" apart relative `to the center I5. A radins maybe selected in g1g" increments for drawing a circle about the center l5for producing circles which vary in diameter g" from each other. Ascale-23 locates the apertures of an adiacent row in 1/2" increments,whiethe apertures of all of the rows locate the point of the -pencil inincrements of 1150). Y I

The semieircular edge I4 may be provided with a protractor scale 24having apertures 25 for receiving the point of a pencil Vfor accuratelyloeating specific pointssuch aszero, thirty, forty. ve, sixty, andninetyr degrees.fk A linear scale 26 is provided along the-edge .-IjIlofthe scale III. A- plurality of apertures "21 extend through the bodyportion of thescale I-Il and are of such -size that a point of apencilwill produce circlesv of diameters from 1/8" up tol/2", in 11gincrements. Y It will be noted that the circles produced by rotating thescale about the center I5 begin with a radius of g so that a 5/84 circleis the -smallest circle may be drawn by rotating a Ipoint about thecenter I5.- With the present scale circles from 1/," to 6" in diameterin 11g" increments may be produced: 'i

I -In Figs. 3. 4 and 5, a further-form of the invention is illustrated.that wherein an aperture 3l! is formed about the center I5 in which ahub 3l is mounted, as illustrated more snecically in Fig. 5. The hub hasthree snaced arms 32 in the -nature of spokes by .which it is secured tothe wall of Vthe aperture in which it isasecured. The spaeebetween thearms is onen to permit the operator to view the point 33 of thecentering pin 34 when applying the point to a surface.

. 4 The centering pin 34 is retained on the center line of the hub by acollar 35 secured thereto above the point 33. A spring 36, mounted abovethe hub -about the pin 34, engages the button 31 on the end of the pinand urges the pin upwardly above the surface on which the scale rests.When the scale is to be employed, it is shifted upon a surface until thepoint 33 is accurately located above the point on the surface. Thebutton 31 is then pressed downwardly to secure the pin in position,after which the scale Il) may be revolved about the pin to generate thecircle in the manner above pointed out in relation to the scale In Figs.6,

7 and 8, a further form of the in- A vention is illustrated, thatwherein the scale 4D -is provided with a tab I6 and centering pin I3.

l The scale 4o has a sint 4| in the portion 42 thereof.-whicli is oisetupwardly to provide a longitudinal recess 43. The under face of thematerial of the recess 43 `may be provided with serrations 5M, asillustrated in Fig. 8. A slide '55 is also provided withserrations-which mate with the serrations 4Q, as illustrated in Fig. 8,and which are clamped together by-a thumb nut 46 operating ona stud 4lsecured to the slide 45 which extends through therslot 4I. Scale reading48 are provided on the surface of the scale lil) having each unitthereof aligned with one of vthe serrations le which thereby accuratelylocates theslide relative to the scale readings. y 'Ilheslide 45contains an aperture 43 for receiving the end of a pencil after theslide has been adjusted to.l locate-the aperture adjacent to theselected scale reading. In other words. theaperture 49 is aligned withthe scale reading which conforms to the radius of the circle-to bedrawn. The thumb screw 46 is then tightened on the stud 41 to securelyclamp the slide in position, with the aperture 43 accurately disposedrelative to thecentering element to conform accurately. to the radius ofthecircle to bedrawn. The plurality of. rowsofapertures 2.1 areeliminated when the reeesslxlfl and slide .45 areemployed. vIn vanyofthe constructions, .an engineering or. protractor scaleis-illustratedwherein the cene, tering point for the circles-.to be .drawn maybe.accurately located and bey securely/maintained in position by downward'pressure applied there#` to. The pencil point, isaccurately located'inan aperture conforming to the radius lof the circle. to 'be drawn,afterrwhiclfiv the scale and pencil arev revolved about the centering`yelement to accurately produce theV circle desired. j

' 'Referring to Figs. 9.' to 1.0, afurthe'r. formjof. the device isillustrated, that whereinthescale. i,has an aperture 5I therein .inwhich a button 52 is snapped and retained within aY-groove 53 inthebutton. Thescale engages the groove-:53

ton is made of transparentinaterial having a convex surface and a iiatface on the latter of which a plurality of concentric rings "Staredisposedin the nature of' a'r'etiele by'which' the' center of thebutton^`and scale may be accuratelyv located. The convexA orsemispheric'al''surface of the button magnifiesfthe distortion producedtothe lines through lthelncentrer' on the surface vas the button ismoved back and` forth thereacross.

No yshifting of the lines is c ibservedV whenthe centers coincide .butany deviation therefrom. ref.: sults in a, magnied-,shiftingpf the linesupandi.

down` 'or to, the ...right and left,.dependingf upon the direction ofmovement of the button and scale. While it was indicated hereinabovethat the apertures 2l and serrations 44 are spaced 1%" apart to producecircles differing 1/8 in' diameter, it is to be understood that gli? orother spacing may be employed to produce circles varyfrom each other anamount more or less than the M3" dimension referred to. 'I'he thumb nut46 alone may be relied upon Without the use of the serrated surfaces forretaining the yslide 45 in adjusted position; or the thumb nutinay beeliminated and the serrated surfaces depended upon for retaining theslide in adjusted position when the instrument is resting upon asurface. The apertures 25 on the protractor scale are located inwardlyfrom the edge, as illustrated in the gures, but it is within the purviewof the invention to have them disposed as notches eX- tending to theedges so that a pencil point may be moved inwardly therein from the edgeto locate the angle.

What is claimed is:

A drawing instrument embodying an elongated element having an apertureand a semi-circular 25 end which is scaled to provide a 180 protractorscribed from the center of the aperture, a locating button comprising agenerally convex transparent lens having a reticle thereon and having aperipheral groove receiving the Wall of the aperture, with the bottomportion of the button projecting beyond the element and the buttonsupported in the aperture in a manner which permits relative rotationwith the element, said element having in the portion remote from saidprotractor additional apertures provided therethrough in predeterminedspaced relation to each other and to the center of said button fromwhich circles may be scribed about the center aligned with the center ofthe button by the use of a lens and reticle portions thereof.

vWILLIAM F. KLEMM.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS

